private void button1_Click(object sender, EventArgs e)
        {
            QLThUOC.DataLayer.KhachHangDATA kh = new QLThUOC.DataLayer.KhachHangDATA();
            DataTable    tbl    = kh.LayDSKhachHang();
            rptKhachHang report = new rptKhachHang();

            report.SetDataSource(tbl);

            CrystalReportViewerKhachHang.ReportSource = report;
        }